Looks like there is a lot of back and forth over the wiping question.
I wiped to condition mine. Then I got a mold problem (not from wiping, I think, I just failed to use propylene glycol), and wiped again with rubbing alcohol to kill any hidden spores. I then reconditioned with another distilled water wipedown. No problems on any of them. Achieved very steady humidities very quickly (1-2 days) with this method.
I think the secret is a DAMP towel, not saturated. The wood does darken slightly, but should NOT have surface moisture sit on it for any extended period. The only way you should get warping is if one area remains significantly wetter than others over an extended time period. This produces a force difference, and actually bends the grain in the wood.
My father is an accomplished woodworker, and has even taken a pro class on the topic of humidity accomodation in fine furniture. The secret is to avoid large moisture gradients, to pay attention to grain directions at joints, and to allow for expansions when the span of wood is long enough to warrant it. The second two should be taken care of by the humi builder, and the humi should be designed to withstand fairly high moisture gradients, since you expect to have ~70% inside and as low as ~10% outside. You just have to make sure you don't SOAK the wood.
As far as staining the wood, it is possible, but if there are no contaminants on the wood surface, and you wipe down evenly, you should get even darkening if any. If one area darkens too much more than others, that means it is accepting moisture more readily, and that is probably not a good thing when you want even moisture exchange all around. The same thing can occur when using woodstain, and the solution is to make sure you wipe evenly, and that the wood is sanded clean of glue and foriegn (such as finger) oils. If there is a grain change, such as at a joint, you can get a color differential, but I usually think this adds to the beauty of well constucted furniture.
My .02!